Automatic telephone system.



8. C. GROH. AUTOMATIC TELEPHONE SYSTEM.

[Nye/woe; 552M420 6. G20 2 APPLICATION FILED IULY 19. \95.

Patented July 2,1918. 3 SHEETSSHEETI Arroewav Mrlvzssss B. C. GROH.

AUTOMAHC IELEPHGNE SYSTEM.

APPLICATIDN mcp SULY :9. m5.

1 ,27 1 ,032. Patented July 2, lens.

3 SHEETS SHEET 3.

ATTOQNE v UNITED STATES PATENT OFFICE.

BERNARD C. GBOH, OF CHICAGO, ILLINOIS. ASSIGN'OR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed July 19, 1915.

To all whom it may concern:

Be it known that I, BERNARD C. Gnon, a citizen of the United States, and a resident of Chicago, county of (look, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the followingis a specification.

My invention relates to automatic telephone systems,'but concerns itself more par ticularly with methods of toll supervision in systems containing one or more automatic exchanges.

In automatic exchanges, it has been customary to provide, in addition to the regu lar automatic apparatus. a multiple jack individual to each line in what is known as a toll switchin section.

A subscriber w o wants a long distance connection operates his dial for the proper number and connects by means of automatic apparatus with a recording operator who obtains the necessary data and passes it to a toll operator. If the party wanted is connected to an automatic exchange the toll operator will now plug into an idle toll line to the distant automatic exchange and, by means of her dial, connect automatically with the line of the wanted subscriber. The toll operator may now order up the number of the calling line at the toll switching section and complete the long distance connection by plugging into the trunk assigned by the toll switching operator.

I have briefly described above one method of handling long, distance calls to an automatic exchange. but modifications will suggest themselves to those versed in the art. For example. the toll op'erator may connect automatically with the calling line thereby dispensing with the toll switching section. ()r the originating exchange may be manual in which case connection will be established by methods common in manual practice and which are well known.

In -any case, it'is extremely desirable, or even necessary, that the toll operator be rovidcd with lamp supervision controlled lly thecalled subscriber in the distant automatic exchange. I

The object of my invention is the pro vision of means whereby a subscriber with .whom connection has been established autospecification of Letters Patent.

Serial No. 40,705.

matically by a distant toll operator over a toll line, may signal the calling toll operator by means of his receiver book.

A further object of my invention is the provision of means whereby a toll line between two automatic exchanges may be used by an operator at either exchange to extend a connection to a subscriber in the other exchange, the calling toll operator having supervision controlled by the called subscriber.

To accomplish these and other useful ends my invention comprises the means hereinafter set forth and claimed.

In the drawings Fi ures 1, 2 and 3 show a complete connection etween a calling substation A in one exchange and a called substation A in a second exchange in a system embodying the principles of my invention. Fig. 4 is a theoretical diagram illustrating these principles more clearly.

Referring to Fig. 1, there is shown at A an automatic substation having at the exchan e the individual line switch C and the multiple jack J. At 0 is shown a toll operator's cord circuit which may be of any approved type. The one shown, however, is very simple comprising, amdng minor elements, the supervisory lamps l and l controlled by relays 34 and 96, respectively, and an operators head set. T which may bc connected to the two stramds of the cord by the key K. For convenience I have shown the answering plug P of the cord circuit 0 as being inserted directly in the niiipic. jack of the calling substation A, although it is understood that in practice the toll operator may complete a connection to a calling substation A in any approved manner as has been explained.

The calling plug 1 of the cord circuit 0 is shown as being inserted in the multiple jack J of a toll line 9 and 10 extending to the distant oliice. Associated with the toll line at the originating oflice is a line switch a repeating coil M, a group of relays I, and a key K. The calling device S may be common to a number of toll lines. Relays 12 and 26 are polarized relays, 11. e., they will not operatively attract their armatures unless current flows through their windings in the right direction.

The toll -linc (91Q) has individual apparatus at the distant exchange similar to Patented July 2, 1918.-

the apparatus at the originating exchange. Referring to Fig. 2, there is shown at N a repeating coil. at l a group of relays, at K at key, at J a multiple jack. and at t" a line switch. At 1) is shown a master switch for cbntrolling a group of line switches such as C, and it is assumed that all other line switches shown are controlled in the same manner by master switches similar to D.

All the line switches shown herein are of the general type of line switch shown in British patent to R. W. James No. 26,301 of 1906, being, however, more nearly of the particular type disclosed in U. 5. Letters Patent No. 1,078,690, granted Jan. 17, 1912, to F. \lewforth.

The master switch D is of the same general type as that disclosed in the above mentioned British Patent No. 26,301 of 1906, being, however, more nearly of the particular. type disclosed in British patent to T. G. Martin, No. 1419 of 1910.

Accessible to the line switch C is a connector switch H (Fig. 3) which is of the same general type as that. disclosed in U. S. Letters Patent No. 815,176 granted March 13th, 1906, to Keith, Erickson and l'lrickson, being, however, more nearly of the particular type disclosed in French Patent No. 466,794 issued March 13th, 1914.

While I have shown the line switch as having direct access to the connector switch H, it may be readily seen that selector switches of any approved type may be inserted between the said line switch and the connector switch in order to increase the capacity of the system. Selector switches which may be. used for the above purpose are of the ty e shown in British patent to T. G. Martin a. 1419 of 1910.

At A is shown an automatic substation having at the distant exchan-ge an indiridual line switch C similar to the switch t. and a multiple jack J.

For the purpose of supplying battery current for talking and for operating the automatic switches I have shown at the origi nating exchange the battery [5 and al the distant exchange the battery B. the two batteries beinggroundedat (1 and (l-". respectively. At R is shown a generator and at Q is shown a bhsy signaling machine.

Inasmuch as the. automatic apparatus illustrated herein is well known in the art and is described in the publications above referred to, it is thought to be. unnecessary to gire more than a general description of the apparatus and operation thereof.

In the following description it will be explained briefly how a connection may be established between the calling substation A in one exchange and 21 called substation A in a distant exchange after-which thermal willbe shown in detail the method by which the subscriber at the called substation may si ma] the toll operator at the originating ol ice.

It will furthermore be shown how the above connection may be established in the reverse diliection, the subscriber at A, in this case, being able to signal a toll operator in the distant otiice.

To obtain a long distance connection the subscriber at A n'iust first get in communication with a recording or toll operator and this may be accomplished by raising the receiver and operating the impulse wheel 4', controlling the impulse springs 7 and 8. in accordance with the proper digit or digits. The line switch and a switch or switches accessible tb it respond to these operations in the well known manner and thereby connection is established between the. substation A and a recording operator. Upon making known his wants the subscriber at substation A is told to hang up for a moment, which he does and lhcrcbv disconnects his automatic apparatus.

The recording operator makes out a ticket containing the required 'iiiformaiion and passes it to a loll operator who will now insert the plug 1' in the multiple jack .l of an idle toll line extending to the desiredexchange. the idle or busy condition of such toll lines being determined by testing with the lip of the plug in the well known man ner. The engagement of the sleeve of plug 1 with the sleeve of jack J closes a circuit including the sleeve relay 36 and the holding winding $37 of the line switch The sleeve relay 3G completes a circuit for the sum-rrisory lamp 1 at conta t 10 and the winding 37, by attracting the armature 15?, disconnects the tip and ring springs of jack J from ground and battery, respectively. at line switch The insertion of plug l also closes contact 4o of jack .l' thereby completing a circuit for relay $59 as follows: ground at G". contact 40, winding of relay 39 to battery. Relay 39, by attracting its armaturcs. completes two parallc circuits which may be traced a's follows: negative. pole of battery li. contact 31. junction of resistance coils 24 and where the circuit divides,.one branch extending by way of resistance coil 24. contact 1H5. armalure 104, contact springs 31! and Fri, windings 20 and 21 of repeating coil M in parallel. lines 5 and 10 in parallel, windings 43 and H of repeating coil N (Fig. ii in parallel, contact springs 50 and 51, armature 49, contact 48, windings '29 and 28 of relay 45 in series to ground at G. while the (ltllUl' branch extends by way of resistance coil through adjustable resistance 13 to ground at (1.

to the junction of resistance 24 with con- 'lhc'polarizcd relay 2G is l bridged across the two parallel circuits described above. one terminal being connected line switch armature 69, the former tact 105 and the other terminal being connected to the junction of the resistance coil 25 with the adjustable resistance 13, the whole forming a W'heatstonc bridge arrangement as shown diagrammatically in Fig. 4. The bridge may be balanced by adjusting the resistance 13 so that no current will ordinarily flow polarized relay 26.

It will be seen that one leg of the VVheatstone bridge circuit traced above includes a simplex circuit which in this particular (lisclosure includes the two sides of a talking circuit in parallel. This simplex ircuit may be traced from the spring 52 of key K in Fig. 1 to'the middle point of windings 20 and 21 of repeating coil M. through said windings in parallel, conductors 9 and 10 in parallel, windings 43 and 44 of repeating coil N Fig. 2, in parallel to spring 50 of key K;

At the distant office the energization of relay 45 completes a circuit for the line relay 54 of line switch C as follows: ground at G", contact springs 55, line 71, winding 57 of repeating coil N, winding of polarized relay 27, armature and contact 59, winding 58 of repeating coil N, line 70, contact springs 56, winding of line rela 54 to batter fiine relay 54 energizes over this circuit and attracting its armature completes a circuit for the pull-in winding 161 as follows: ground at G, armature 1G4. contact 163,

ull-in winding 161, contact 162 to battery.

he energization of the pull-in winding attracts the plunger arm 60 and the cut-off by means of its plunger (not shown) forcing the springs 61, 63, and 67 into engagement with the contacts 62, 64, 66 and (i8, rcs]n'cti\'el v, and the latter separating the pair of contact springs '56 and the pair of contact springs 55, thereby breaking the circuit of the line relay 54..

The engagement of springs (31 and 67 with contacts 62 and (58. respectively, coinpletes a circuit for the line relay 72 of the connector H as follows: ground at G, lower winding of line rclay 72. contact springs 174 and 175. line 16. contact 68, Spring 67, line 71. winding 57 of repeating coil N, winding of polarized relay 27, armature and contact 5!), winding 58 of repeating coil N, line 70, spring (51. contact 0-2, line 14, contact springs 17] and 172, upper winding of line relay 72 to battery. I pon energizing. the line relay 72 completes a circuit for the slow acting relay 73, which in turn completes a holding circuit for the over the following path: ground at (i', contact springs 74, wire 15. contact (34, spring (33,- holding winding 160 to battery. The line relay 54 is slow acting and retains its armature until after the in the winding of the circuit has been established. A branch of extends from the junction of win ing 160 and spring 63 to the multiple jack J where a guarding potential is placed on the sleeve. Two circuits have been described already, that of the line relay 54 now broken, and the present circuit of the line relay 72, which include the polarized relay 27. The direction of the current in relay 27 is such, however, that the lower end of armature 1!}?! is attracted thereby holding Contact 93 o aen. ,The foregoing operationsof relays at I and F and the operation of line switch C and relays of connector H have taken ilace in response to the insertion of plug in jack J ing ofl'iee is nowready to dial the number wanted but first she must actuate the key K thereby substituting the impulse "springs of the calling device S for the resistance coil 24 in the circuit of the relay 45 (relay group F). Relay 45 remains energized but the balance of the wheatstonc bridge is destroyed and current flows through the winding of polarized relay 26 as follows: ground at G, adjustable resistance 13, winding of relay 26, winding of resistance coil 24, contact 31 to battery. The effect upon relay 26 produced by current flowing as described above is such, however, that the lower .end of armature 147 is attracted. therebyholding contact 47 open. i

The operator may now 0 )erate her dial for the first digit of the desired number [hereby separating a number of times the impulse springs of the calling device S and causing corresponding deenergizations of the relay 45. At each deiinergization of the relay 45 the line relay 72 of the connector I] retracts its armature and sends an, impulse to the slow acting relay 76 and the vertical nuignct- 75 in series, the slow acting relay 73 keeping its armature attracted nmanwhilc. The vertical magnet raises the shaft carrying the wipers 175, 105' 2111(11155 The toll operator at the orginatuntil the wipers stand opposite the horiiontal level of contacts in \\'lll('l1 are located the contacts of the desired line. The slow acting relay 76, in serieswith the vertical magnet, holds its armature attractedduring the series of impulses arid in its energized position closes a circuit of the private magnet 79. At the end 'of the series of impulses the relay 76 retracts its armature whereupon the circuit of the private magnet 79 is broken and it deiincrgizes thereby allowing the side switch wipers to more to their second position in the well known manner.

The operator may now operate her dial for the last digit of the desired number resulting as before in 'dei nergizations ofthe line relay 72 which now (the side switch battery and ground at line switch C.

1 respectively.

pulses to the slow acting relay 76 in series with the rotary magnet 81. The rotary magnet rotates the shaft until the wipers 175. 105 and 185 rest upon the bank contacts 187, S7 and 197 of the line extending to substation A. The slow acting relay 7th by actuating the. private magnet as be- A circuit may be traced from contact 87 through holding winding 83 of line switch (1'. \Vinding 83 is energized over this circuit and, by attracting the'cnt-ofl' armature, disconnects the lilies of substation A frolm '1 10 wires 14 and 16 are connected by the side switch wipers 84 and 85. in their third position with the line wipers 175 and 185. The side switch wiper 80 in its third position completes the circuit of the ringing relay 88 in series with the interrupter 89 whereupon the ringing relay is actuated intermittently to ring the bell at substation A. i

The operator may now restore her key K thereby cutting out the calling device S and restoring the normal balance of the bridge.

She may also. at this time insert the plug 1" in the multiple jack J of the calling subscriber at substation A. and if the subscriber has not already'relnovcd his receiver she may ring his hell by actuating a ringing key (not shown) which may be included in her cord circuit. The engagement of the sleeve of plu 1 with the jack J completes a circuit including the sleeve relay 33 and the holding winding 38 of line switch C. The sleeve relay 33 closes at its contact 102 the circuit of the supervisory lamp 1; and the holding winding 38, by attracting the cut-off urinal ure 156, disconnects the calling line from battery and ground at the line switch C.

We are now ready to consider the super visory lamps l and 1' whose circuits have been completed by sleeve relays 33 and 36 v The supervisory lamp 1 is controlled by the subscriber at substation A through the medium of the double wound relay 34 in a manner made evident from the drawing.

The supervisory lamp Z is controlled by the subscriber at substation A through the medium of means provided by iny invention and in a manner which" may be described as follows: Upon the removal of the receiver at substation A a circuit is completed for the double wound back bridge relay 90 of the connector H.which relay is provided for feeding talking battery to the called subscriber.

Relay 90 upon attracting its armature, completes a circuit of the ring cut off relay 91 thereby stopping the ringing, and also reverses the battery connections to wires 14 and 16 thereby reversing the direction of current How in the polarized relay 27. The eli'ect of the current is now such that the upper end of armature 193 is attracted ground at (2 contact'93, winding 29 of rcay '45, contact 48., arluatm'e 49, contact springs 51 and 50, windings 43 and 44 of repcating coil N in parallel. lines 9 and 10 in parallel. windings'ZU and 21 of repeating coil M in parallel, contact springs 52 and 32, armature 104, contact 105, winding of polarized relay 26, resistance coil 25, contact 31 to battery. Current flowing in the direction described above in relay 26 is such that the armature H7 is broughtinto engagement with contact 47 thereby short circuiting the condenser 95'.

The double. wound relay 96 is now energized over the following path: ground at G. upper winding of relay 96, ti.p of plug P". tip sprin r of jack J winding 23 0 repeating coil 1. contact 47, armature 147. winding 22 of repeating coil M, ring spring of jack J'-'. ring of plug I, lower winding of relay 9G to battery. Upon attracting its armature. relay 96 breaks the circuit of the lamp 1 at. contact 97 thereby extinguishing the lamp and indicating to the operator that the subscriber at the distant exchange has answered. \Vhen the conversation is finished the subscribers at substations A and A will hang up their receivers, whereupon the circuits described above for relays 34 and 99 will be broken and these relays will retract' their armatures:thereby again completing the circuit of the supervisory lamps l a. L 1'.

Upon observing the lights burning the operator knows that the conversation is finished and therefore she removes the plug.-: 1" and P from the jacks. Ipon the removal of plug 1 the contact 40 is opened breaking the circuit of relay 39. Upon the dei nergization of relay 39 the circuit of relay 45 is broken. Relay 45, by retracting its armature breaks the circuit of line relay 72 of the connector II whereupon the automatic apparetifkuseddn the distant exchange 18 restored to normal in the well known manner.

I have assumed in the foregoing description that the called substation A was idle when called. If it had been busy the conswitches are adapted to connect with a group jack J (Fig. 3.) with amnesia nector H would have operated, after the last series of impulses, to connect the busy signaling nacliine I with one side of the calling line, the side switch wipers being held in the second position for this purpose.

The calling subscriber, on hearing the bus si nal n s u) his receiver. thereb' b l giving the operator a disconnect s gnal as the case it is evident that the subscriber at substation A will be able, through the me dium of a toll o erator, to obtain a connection with the su scriber at substation A in the distant exchange, whereupon the toll operator will have supervision controlled by the subscriberat substation A. scribe briefly how this is done. i

The toll operator at the exchange to which A. is connected is provided with .cord circuits similar to the cord circuit shown at 0 (Fig. 1) by means of which she can connrc the/line of substation A at the multiple the jack J (Fig. 2) of the toll line to the distant exchangle. The operation from now on is exactly t e same as previously. described it being understood. that the line switch C? in Fig. 1 has access to connector switches such as connector H shown in Fig. 3 exceptthat said connector of lines of which the line of substation A I is one.

The supervision is taken care of by a Wheatstone brigge arrangement similar to the one describ and inasmuch as the aparatus at the two ends of the toll line are in duplicate it is tho 'lit to be unnecessary to further ani lify the explanation. It will bereadily un erstood that my system of toll be used on toll lines extending from a manual to an automatic exchange in which case the apparatus need not' be in duplicate.

60 a second circuit, a relay in said While I liaye described one f01'm in which my invention may be practised I do not wish to be held strictly ,to the apparatus and method shown herein, but desire to include all mod fications which may come within the scope the appended claims.

Wli t1]: claim as my invention is:

1. "In a telephone system, a first circuit, a signal in said circuit, a ,Vheatstone bridge, said signal under the control of said bridge, second cir cuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit.

2. Ina telephone system, a first circuit,

I will derelaywhereby said signal in said circuit, a said signal under the control of said bridge, 95

a si nal in said circuit, a Wlieatstone bridge, 66-

said signal under the control of said bridge, a second circuit, a relay in said second cir cuit, said bridge under the control of said relay whereby said signal may be operated over said second seconcbcircuit for operating said relay.

3. In a telephone system a first circuit, a signal in said circuit, a eatstone bridge, said signal under the control of said bridge,

a second circuit, a relay in said second an cuit, said bridge under the control of said relay whereby said signal may be operated over said second ,CllCUlil, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit. p 4. In a telephone system, a first circuit, a signal in said circuit, a. ,Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said cuit, said bridge under the control of saidsignal may be operated circuit, a third circuit,

" second and third over said second said means for connecting circuits and for controlling said relay from said third circuit, said means comprising an automatic progressively movable switch.

5. In a telephone system, a first circuit, a Wheatstone bridge,

a second circuit, a relay in said second circuit, said bridge under the controlof said relay whereby said signal may beoperated over said second circuit, a third circuit,

means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of progressively movable trunking switches.

6. In a telephone system, a first circuit, a

a Wheatst-one bridge,

signal for said circuit, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the

balance of said bridge under the control of 11o said relay whereby said signal may be oper-' ate'd from said second circuit.

7. In a telephone system. a first ircuit, a signal for said circuit, a \Vlieatstonl; bridge, said signal under across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated ironr said second in said second circuit for operating said relay.

8. In a telephone system, a first circuit, a signal for said circuit, a Wlieatstono bridge, said signal under across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of circuit, and means in said 70 second. on 85 the control of! a relay circuit, and means the control of a relay said relay whereby said signal may be operated-from said second circuit, a third circuit, means for connecting said second and third circuits and t'or controlling said relay from said third circuit.

9. In a tele )hone system. a first circuit, a signal for said circuit. a \Vbeatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of saida'elay whereby said signal may be operated from said second circuit, a third cirenit, means for connecting said second and third circuits and for controlling said relay .from said third circuit. said means comprismg an automatic progressively movable switch.

10. In a telephone systenna first circuit.a signal for said circuit. a 'hcatstone bridge. said signal under the control of a relay across the branches ot' said bridge. a second circuit. a relay in said second circuit. the balance of said bridge under the control of said relay whereby said signal may he operated-from said second circuit. a third circniti means for connecting said second and third circuits and for controlling said relay from said third circuit. said means comprising-a plurality of progicssively movable trunking switches.

11. In a telephone system.a tirst circiiit. a signal for said circuit, a \Vheatstone bridge. said signal under the control of a relay across the branches of said bridge. a second circuit. apolarized relay in said second circuit. the. halance of said bridge under the control (it said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse directi n.

12. In a telephone system. a first circuit. a isignal for said circuit. a \Vhe'atstone bridge. said signal umler the control of a relay hcross the branches of said bridge. a second ircuit. a relay in said second circuit. the balance of said br dge under the control of Said relay whereby said signal may be oper- Atgd from said second circuit. and means in SAid second circuit for reversing the direction of the current flow.

13. In a telephone system. a first circuit. A signal for said circuit. a Wheatstone bridge. said signal under the control of a My across the branches of said bridge. a SECOnd circuit. a relay in said second circuit. {in balance. of said bridge under the control OF Said second relay whereby said signal MAY be. operated from said second circuit. a tzhifld circuit. means for conne ting said secdviO aml third circuits and for reversing the cllrtction of current lion in the second circ it or operat ing said second relay.

in a telephone system. a first A Signal for said circuit, a

cin'uit. \Vhca t stone bridge, said signal under the control of a relay across the branches of said'bridge. a second circuit, a. polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second cir cuit with current in one direction but, not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay. from said 76 third circuit, said means comprising an automatic progressively movable switch.

15. In a telephone system, :rfipst circuit, a. signal for said circuit, a Wheatstone bridge, said signal under the control of n'relay 80 across the branches of saidbridge, a second circuit. a olarized relay in said second cir-' cuit. the balance of said bridge under the control of said relayh hereby said signal may be operated from isaid second circuil: 8 5f with current in one direction but not, in the reverse direction, a third circuit. means for connecting said second and thirducircuits f and for contmlling said relay from said third circuit. said means comprising a phr rality of progressively muvable trluiking switches. 7 v

Hi. In a telephone system. a first circuit, a signal for said circuit. a \Vhcatstone bridge, said signalauuler the controlofa relay across the branches of said bridge, -a second circuit. a polarized relav in said second eir- R n mat. the balance of said bridge under the control of said relay wherebysaid signal. may be operated from said second circuit with curreutin one direction but not in the reverse-direction. a telephone associated with the first circuit. a telephone associated with the second circuit. and a talking circuit connecting the two. said. talking circuit included in one leg of said bridge.

17. In a telephone system, a first circuit,

a signal for said circuit. a Wheatstone. bridge. said signal under the control of a relay across the branchcs of said bridge. a second circuit. a polarized relay in said second circuit. the balance of said bridge under the control of said rela'y whereby said signal may be operated 'from said second circuit with current in one direction but not in the reverse direction. a third circuit. means for connecting said second and third cir'uitsand For controlling said relay from said third circuit. said mea is comprising an automatic progres ively ltt ffl'tllllt switch. a telephone 0 assm'iated with the lilstcirclllt. a telephone associated with the second circuit. a talking circuit connecting the two. said talking cireuit included in one leg of said-hritlge,"and means for operating said automatic switclrl2fi over the two sides of the talkingcircnitdn said leg in multiple. r:

18. in a telephone system. a first circuit. a signal for said circuit. a Wheatstone bridge. said signal under the control of a relay actose across the branches of said bridge, a second circuit, a gglarized relay in said second circuit, the lance of said bridge under the control of said relay wherebysaid signal may be operated from said second circuit with current in one direction but not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of progressively movable trunkin switches, a telephone associated with the first circuit, a te ephone associated with the second circuit, a talking circuit connecting the two, said talking circuit included in one leg of said bridge, and means for operating said automatic switches over the two sides of the talking circuit in said 1c in multiple. 19. In a telephone system, a rat circuit, a signal in said circuit, a Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge under the control of said relay whereby said si nal may be operated over said second circuit, a talking circuit extending over one leg of said bridge, and an adjustable resistance in one leg of the bridge whcreb the bridge may be adjusted in balance w en the resistance of the talking circuit varies.

20. In a telephone system, a first circuit, a signal, in said circuit, a Whcatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second c1rchit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a talking circuit extending over one leg of said bridge, means in said second circuit for operating said relay, and an adjustable resistance in one leg of the bridge whereby the bridge may be adjustcd in balance when the resistance of the talkin circuit varies.

21. n a telephone system, a first circuit, a signal in said circuit, a Whcatstonc bridge, said signal under the control of said bridge, a second circuit, a relay in said sccond Cl!" cuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a thi d circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, a talking circuit extcnding over one leg of said bridge, and an ad justabk resistance in one log of the bridge whereby the bridge may be adjusted in balance when the resistance of the talking circuit varies;

22. in n telephone system, a first circuit, a signal in said circuit, a Whcatstonc bridge,

said signal under thccontrol of said bridge,

a second circuit,.a relay in said second,circuit, said bridge under the control ofi said relay whereby said signal may be operated over said second circuit, a third circuit,

means for connecting said second and third circuits and for controllingsaid relay from said third circuit, said means comprising an automatic progressively movable switch, a talking circuit extending over one leg of said bridge, and an adjustable resistance in one leg of the bridge whereby the'bridge may be adjusted in balance when the resistance of the talking circuit varies.

23. In a telephone system, a first circuit, a signal in said circuit, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge'under the control of said relay whenby said signal may be operated over said second circuit, a third circuit, means for connecting said secondand third circuits and for controlling said relay from said third circuit, said means com rising a plurality of progressively movabe trunking switches, a talking circuit extending over one leg of said bridge, and an ndjust able resistance in one leg of the bridge whereby the bridge may be adjusted in balance when the resistance of the talking cir cuit varies.

24. In a telephone system, a first circuit, a signal for said circuit, a \Vheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit; the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising an automatic progressively movable switch, ti. telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a line relay in series with both sides of said talking circuit in multiplc, said talking circuit and relay in one leg of said bridge, and

-mcans for operating said rclay over said talking circuit for controlling said automatic switch.

25. In a telephone system, a first circuit, a signal for said circuit, a ivhcatstonc bridge, said signal under the control of a relay acrossihc branches of said bridge, a second circuit a polnrizcdd'elay in said second circuit, the balance of said bridge undcr the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said'relay from said third circuit, said means comprisinga plurality ,of progressively movable trunking switches, a title hone associated with said first circuit, a te ephone associated with said second circuit, a talking circuit connecting the two, a line relay in series with both sides of said talking circuit in multiple, said talk ing circuit and relay in one leg of said bridge, and means for operating said relay over said talking circuit for controlling said automatic switches.

26. In a telephone system, a signal, a lVheatstone bridge for controlling said signal, a line, said bridge under the control of said line for controlling said signal.

27. In a telephone system. a signal, a I'Vheatstone bridge for controlling said signal, a line, a i'nagnefin s'z'iidline, said bridge under the control of said magnet for controlling said signal.

28. In a telephone system, a signal, a Vl'heatstone bridge for controlling said signal, a line, a magnet in said line, saidbridgc undr the control of said magnet, a source of current in circuit with said line and magnet for supplying a How of current in the line in one direction, and means for rcrcrsing'the direction of flow in the line for controlling said magnet. bridge and signal.

29. In a tele hone system, a signal, a \Vheatstone. bri go for controlling said signal, a line, a polarized magnet in said line, said bridge under the control of said magnet, a source of current in circuit with said line and magnet for supplying a flow of current in the line in one direction, and means for reversing the direction of flow in the line for controlling said magnet, bridge and signal.

30. In a tele hone system, a signal, a VVheatstone bri ge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch. a second line for controlling said relay, said second line and relay included in one. leg of the bridge, and means in said first line for controlling said leg to control said signal.

31. In a telephone system, a signal, a IVhcatstonc bridge for controlling said sig nal, a line. an automatic progressively morable switch in said line, a line relay for controlling said switch, a second line. for controlling said rclay,said second line and relay included in one leg of the bridge, and means in said first line for controlling said leg to control said signal.

32. In a telephone system, a signal. a

lVheatstonc bridge for controlling said signal, a line. a switch for said line, a line relay for controlling said switch, a second line for controlling said relay, said second line and relay included in one leg of the bridge, and means in said first line for unbalancing said leg to control said signal.

33. In a telephone system, a signal, a Wheatstono bridge for controlling said signal. a line, a. switch for said line. a line relay for contri'illingsaid switch, a second linev for controlling said relay, said second line and t relay included in one leg of the bridge, and means in said lirst line for varying the resistance of said relay to "unbalance said leg to operate said signal.

In d" telephone system, a signal, a \Vhcatstone bridge for controlling .aid sig-. nal. a line, a switch in said line, a line relay for controlling said switch, a talking circuit a simplex circuit superimposed upon said talking circuit. said relay eontrolhal over said simplex circuit, means for connectin said'relay in one leg of said bridge, ant means for varying the resistance of said rclay to unbalance said bridge to affectv said signal.

35. In a telephone system, a signal, a Wheatstone bridge for controlling said sig' nal. a line, a second line, means for con necting said two lines, said bridge under the control of said second line over said first line for controlling said signal.

an. In a telephone system, a first circuit, a signal in said circuit, a \Vhcatst'one bridge, said signal under the control of said bridge, a second circuit, a relay in the second circuit, said bridge under the control of said relay whereby said signal may be operatcd ovcr said second circuit. a, telephone associated with the first circuit. a telephone associated with the second circuit, a talking circuit connecting the two. a. section of said talking circuit. included in one leg of said bridge.

37. In a telephone system, a first circuit, a signal in said circuit, a IVheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit. said bridge under the control of said relay whereby said signal may be operated over said second circuit, and means in said second circuit for operating said relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the. two. a section of said talking circuit included" in one leg of said bridge.

238. In a telephone system, a first ciigcuit, a signal in said circuit, a VVheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge umler the control of said relay whereby said signal may be operated over said second circuit, a third circuit, means for conuectii'ig said second and third circuits and for controlling said relay from said third circuit. a telephone associated with the lirst circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg of said bridge.

:15). In a telephone system, a first circuit. a signal in said circuit. a \Vheatstone bridge, said signal under the control of said bridge, a second circuit. a relay in said second circuil. said bridge under the control ol said ,relay whereby said signal may be operated over said second circuit, a third circuit means for connecting said second and thir circuits and for controlling said relay from said third circuit, said means comprisin an automatic progressively movable switci, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg of said bridge.

40. In a telephone system, a first circuit, a signal in said circuit, a VVheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprisin a plurality of progressively movable trunking switches, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg of said bridge.

41. In a telephone system, a. first circuit, a signal for said circuit, a VVheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control ol said relay whereby said signal may be operated from said second circuit, a. telephone associated with tho first circuit, a telephone associated with the second circuit, a talking circuit conncctii'ig the two, a vsection of said talking circuit. included in one leg of said bridge.

42. In a telephone system. a first tl 'tilli. a signal for said circuit. a \Viicai ofnic bridge. said signal under the control of a relay across the branches of said bridgc, a second circuit, a relay in said second circuit. the balance of said bridge under th control oi said relay whcrclrv said signal inay,bc operated from said second circuit. and means in said second circuit for operating said relay. a telephone associated with tho first circuit. a t lephone associated with the second circuit. a talking circuit connecting the two, a section of said talking circuit included in one log of said bridge.

43. In a telephoni-systcm, a first circuit, a signal for said circuit, a lVl'ieatstonc bridge. said signal under the control of a. relay across the branches of said bridge, a second circuit. a relay in said second circuit. the lndz'nice oi said l" 'idge under the control of said relay whereby said signal may be operated iromsaid second circuit, a third circuit. means for connecting said second and third circuits and for controlling said relay from said third circuit. a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a. section of said talking circuit included in one leg of said bridge.

4,4. in atclephone system, a. first circuit, a signal for said circuit. a \Vheatstone bridge, said signal under the control of a. relay across the branches of said bridge, a second circuit, a relay in said second-circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising an automatic progressively movable switch, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg of said bridge.

45. In a. telephone system, a first circuit, a signal for said circuit. a \Vhcatstone bridge. said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit. a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of progressircly movable trunking switches. a .telephone associated with the first circuit a telephone associated with the second clrcult, a talking circuit connecting the two, a section of said talking circuit included in one leg of said bridge.

46. In a telephone system, a first circuit, a signal for said circuit, a. \Vheatstonc bridge, .rxid signal under the control of a rclay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the cont rol of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction. a telephone associated with the first circuit, a telephone associated ith the second circuit, a talking circuit; connecting the two. a secti n of said talkin; circuit included in one leg of said bridge.

47. in a. telephone systrin. a first circuit, a signal for said circuit. a W'hcatstonr bridge. said signal under the control of a relay across the branches of said bridge. a second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may he operated from said second circuit, and means in said second circuit for reversing the dircc tion of the current How, a telephone asso ciated with tho first circuit. a telephone a sociated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg of said brid e.

4,8. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said brid e under the control of said second relay w ereby said si a1 may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for reversing the direction of currentfiow in the second circuit for operating said second relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg of said brid e.

49. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising an automatic progressively movable switch, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, a section of said talking circuit included in one leg, of said bridge.

50. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, sald signal under the control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of progressively movable trunking switches, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two. a section of said talking circuit included in one leg of said bridge.

51. In a telephone system, a first circuit, a signal in saidcircuit, a Wheatstone bridge, said signal under the control of said bridge, asecond circuit, a relay in said second circuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a telephone associated with the first circuit, a telephone associated with the second circuit, a talkin circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

52. In a telephone system, a first circuit, a signal in said circuit, a Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, and means in said second circuit for operating said relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talkin circuit connecting the two, said talking clrcuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

53. In a telephone system a first circuit, a signal in said circuit, a Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge under the control of said over said second circuit, a third circuit,

means for controlling said second and third circuits and for controlling said relay from said third circuit, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit 'divided into sections, one section of said talking cir cuit included in one leg of said bridge, said signal associated with a second section.

54. In a. telephone system, a first circuit, a si al in said circuit, a Wheatstone bridge, sai signal under the control of said bridge, a second circuit, a relay in said second circuit. said bridge under the control of said relay whereby said signal may be operated over said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising an automatic progressively movable switch, a telephonb associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one seelion of said talking circuit included in one leg of said bridge, said signal associated with a second section.

55. In a telephone system, a first circuit, a signal in said circuit, a Wheatstone bridge, said signal under the control of said brid a second circuit, a relay in said second circuit, said bridge under the control of said relay whereby said signal may be gpcrated over said second circuit, a third'fmrcuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a lurality of progressively movable trunk mg switches, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talkin circuit includedv in one leg of said bridge, said signal associated with a second section.

56. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridge. said signal under the control of a relay across the branches of said bridge, a. second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay wherebysaid signal may be operated from said second circuit, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talkin circuit divided into sections, one section oit said talking circuit included in one leg of said bridge, said signal associated with a second section.

57. In a telephone system, a first circuit, a signal for said circuit, a Vl'heatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit, and means in said second circuit for operating said relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one le of said bridge, said signal associated with a second section.

58. In a telephone system, a first circuit, a signal for said circuit, a VVhcatstone bridge. said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay whereby saidsignal may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, a telephone asso ciated with the first circuit, a telephone associated with the second circuit, a talking eircuit connecting the two. said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

59. In a telephone system, a first (lllClllL, a signalfor said circuit, a 'Wheatstono bridge, said signal under the control of a relay across the branches of: said bridge, a. socmld circuit, a relay in said second circuit. the balance of said blldgc under the control of said relay whereby said signal may be opcrated from said second circuit, a third circuit, means for connecting Said second and third circuits and for controlling said relay from said third circuit, said means comprisin an automaticprogressively movable switci, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with second section.

60. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge...nder the control of said relay whereby said signal maybe operated from said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of progressively movable trunking switches, a telephone associatcd with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

6]. la a telephone system, a. first circuit, a. signal for said circuit, a \Vheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a telephone associated with the first circuit, a telephone associaled with the second circuit, a talking circuit connecting the two. said talking circuit divided into sections. one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

(32. in a telephone system, a first circuit, a signal For said circuit. a heatstonc bridge. said signal under the control of a. relay across the branches of said bridge, a second circuit, a relay in said econd circuit, the balance of said bridge under the control of said relay \\'liercb said signal may be operated from said second circuit. and n inns in said second circuit for reversing the direction ol' the current. tion. a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two. said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

63. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of said second relay whereby said signal may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for reversing the direction of current flow in the second circuit for operating said second relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talkin circuit divided into sections, one section 0 said talking circuit included in one leg of said bridge, said signal associated with a second section. I

64. In a telephone system, a first circuit, a. signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising an automatic progressively movable switch, a telep' -ne associated with the first circuit, a tele phone associated with the second circuit, a talking circuit connecting the two, said talk ing circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

65. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of prom'essively movable trunking switches, a tee hone associated with the first circuit, a te ephone associated with the second circuit, a. talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section.

66. In a telephone system, a first circuit a signal in said circuit, a Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in the second cir cuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

67. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridge, said signal under the control of said brid e, a second circuit, a relay in said second c1rcuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, and means in said second circuit for operating said relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

68. In a telephone system, a first circuit, a signal in said circuit, a Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, a telephone associated with the first circuit, a telephone associated with the first 0nd circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

69. In a telephone system, a first circuit, a signal in said circuit, a Wheatstone bridge, said signal under the control of said bridge, a second circuit, a relay in said second circuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprisingan automatic progressively movable switch, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talkin circuit divided into sections, one section 0% said talking circuit included in one leg of said bridge, said signal associafiad With a second section, said relay associated with a a third section.

In. In a telephone system, a first circuit. a signal 1n said circuit, a Wheatstoile bridge,

said signal under the control of said bridge, a second circuit, a relay in said second cir cuit, said bridge under the control of said relay whereby said signal may be operated over said second circuit, a third circuit, means for connecting said second and third circuits, and for controlling said relay from said third circuit, said means comprising a plurality of progressively movable trunking switches, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit in cluded in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

71. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a rela in said second circuit, the balance of sait bridge under the control of said relay whereby said signal may be operated from said second circuit, a telephone associated with. the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talkin circuit divided into sections, one section 0 said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

72. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit, and means in said second circuit for operating said relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

73. In a telephone system, a first circuit, a ,signal for said circuit, a iVheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit a relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit, a third circuit, means for connecting, said second and third circuits, and for controlling said relay from said third circuit, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the too, said talkin circuit divided into sections, one section 0? said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

74. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit a relay in said second circuit the balance oi said bridge under the control of said relay whereby said signal may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprisin an automatic progressively movable switc 1, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections one section of said talking circuit include in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

75. In a telephone system, a first circuit, a signal for said circuit, a \Vheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit a relay in said second circuit, the balance of said bridge under the control of said relaywhereby said signal may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means comprising a plurality of progressively movable trunking switches, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

76. In a telephone system, a first circuit, a signal for said circuit, a \Vhcatstonc bridge, said signal under line control of a relay across the branches of said bridge, a second circuit, a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the reverse direction, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuit divided into sections, one section of said talking circuit included in one legof said bridge, said signal associated with a second section, said relay associated with a third section.

77. In a telephone system, a first circuit, a signal for said circuit, a VVheatstone bridgesaid signal under the control of a relay across the branches of said bridge, a second circuit, a relay in said secondcircuit, the balance of said bridge under the control of said relay whereby said signal ma be operated from said second circuit, an means in said second circuit for reversing the direction of the current flow, a tele phone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talkin circuit divided into sections, one section 0% said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

78. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit, a role. in. said second circnit, the balance ofsaid bridge under the control of said second relay whereby said signal may be operated from said second circuit, a third circuit, means for connecting said second and third circuits and for reversing the direction of current flow in the second circuit for operating said second relay, a telephone associated with the first circuit, a telephone associated with the second circuit, a talking circuit connecting the two, said talking circuitdivided into sections, one section of said talking circuit included in one leg of said bridge, said signal asso ciated with a second section, said relay associated with a third section.

79. In a telephone system, a first circuit, a signal for said circuit, a Wheatstone bridge, said signal under the control of a relay across the branches of said bridge, a second circuit. a polarized relay in said second circuit, the balance of said bridge under the control of said relay whereby said signal may be operated from said second circuit with current in one direction but not in the rcvcrsc direction, a third circuit, means for connecting said second and third circuits and for controlling said relay from said third circuit, said means coinprisin an auto inatic progressively movable switc a telephone associated with the first circuit, a tele phone associated with the second circuit, a talking circuit connecting the two. said talkino circuit divided into sections, one section 0? said talking circuit included in one leg of said bridge, said signal. associated with a second section said rclay associated with a third section.

80. In a telephone system, a first circuit. a signal for said circuit, a Wheutstonc bridge, said signal undcr the control of the relay across the branches of said bridge, a second circuit, a polarizcd rclay in said Second circuit, the balance of said bridge under thc control of said relay whereby said signal talking circuit divided into sections, one section of said talking circuit included in one leg of said bridge, said signal associated with a second section, said relay associated with a third section.

81. In a telephone system, a signal, a

Wheatstone bridge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch, a line in said bridge for controlling said relay, said bridge under the control of said first line for controllin said signal.

82. In a telephone system, a signal, a Wheatstone bridge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch, a controlling circuit including the relay winding for controlling said rclny, a section of said controlling circuit forming part of said bridge, and means in said line for varying the re sistance oi the controlling circuit for controllin said signal.

83. n a telephone system, a signal, a Whcatstone bridge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch, a controlling circuit including the relay winding for controlling said relay, a section of said controlling circuit forming part of said bridge, and means in said line for varying the resistance of the controlling circuit for controlling said signal, said controlling circuit including a talking circuit.

84. In a telephone system, a signal, a Wheatstonc bridge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch. a controlling circuit including the relay winding for controlling said relay, a section of said controlling circuit forming part of said bridge, and means in said line for \a'rying the resistance ol' the controlling circuit for controlling said signal, said controlling circuit including a talking circuit, both sides of which are conncctcd in multiple.

85. In a telephone system, a signal, a 'hcatstonc bridge for controlling said signal, a line. a switch in said line, a line rclay for controlling said switch, a controlling circuit including the relay winding for controlling said rclay. a section of said controlling circuit forming part of said bridge, lucans in said line for rnryin r the resistance of the controlling circuit or controlling said signal, an impulse sender and means for including the impulse sender in said controllin circuit.

86. n a telephone system, a signal, a Wheatstone bridge for controlling said sig 119.1, a line, a switch in said line, a line relay for controlling said switch, a controlling circuit including the relay winding for controlling said relay, a section of said controlling circuit forming part of said bridge, means in said line for varying the resistance of the controlling circuit for controlling said signal, said controlling circuit including a talking circuit, an impulse sender and means for including the impulse sender in said controlling circuit.

87. In a telephone system, a signal, a Whcatstone bridge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch, a controlling circuit including the relay winding for controlling said relay, a section of said controlling circuit forming part of said bridge, means in said line for varying the resistance of the controlling circuit for controlling said signal, said controlling circuit including a talking circuit, both sides of which are connected in multiple, an impulse sender and means for including the impulse sender in said controlling circuit.

88. In a telephone system, a signal, a \Vli'catstone bridge for controlling said signal, a line, a switch in said line, a line relay for controlling said switch, a controlling circuit including the relay winding for controlling said relay, a section of said controlling circuit forming part of said bridge, means in said line for varying the resistance of the controlling circuit for controlling said signal, said controlling circuit including a talking circuit. an impulse sender and means for switching said controlling circuit into connection with said impulse sender, said talking circuit including an inductive coil. said line relay having one side connected to the midpoint of said coil \vhcrcby impulses from said impulse sender for operating said relay do not att'cct the talking circuit or interfere with the talking.

H9. lo a telephone system. a signal. a \\'healstone bridge for controlling said signal, a line. a switch in said line, a line relay for controlling said switch. a conlrtlliug circuit including the rclav winding for corn trolling said relay. a section of raid controlling circuit l'ormiug part of said bridge, means in said line For varying the resistance oi the conlrolling circuit for controlling said signal. said controlling circuit in cluding a talking circuit. both sides ol which are connected in multiple. an impulse sender and means for switching said controlling circuit into connection with said impulse sender, saidtalking circuit includ-' ing an inductive coil, said line relay having one side connected to the mid-point of said coil whereby impulses from said impulse sender for operating said relay do not affect the talking circuit or interfere with the talking.

90. In a telephone system, a signal, a pair of conduc ors connected in multiple across the terminals of a battery, a signal controlling relay bridged across said multiple at points of like potential dividing the multiple into four sections, a line, a switch for said line, a line relay for controlling said switch, a second line for controlling said relay, said second line and relay included in one of said sections, and means in said first line for varying the. resistance of said section to raise the potential of one of said points over theother to operate said signal relay to control said signal.

91.. In a telephone system. a first circuit, a signal in said circuit, a pair of conductors connected in multiple across the terminals of a battery, a signal relay bridged across said multiple at. points of like potential, a second circuit, a relay in said second circuit, the relative potential of said points lander the control of said last relay whereby the potential of one of said pointsis raised above the other to control said signal from said second circuit.

92. In a telephone system, the combination with a trunk line and an automatic switch for connecting calling and called lines, of an operating circuit for said switch comprising the two sides of a portion of the talking conductors of said trunk line in parallel, a source of current for said circuit. and a signal controlled by the called line by increasing the current flow in said circuit.

93. In a telephone system, means for connecting calling and called lines including a trunk line and an automatic switch, an operating circuit for said switch comprising the two sides ot' a portion of the talking conductors of said trunk line in parallel. a source of current for said circuit, and a signal controlled from the callcd line by altering the current How in said circuit.

Sit. Tn a telephone system. means for conncctillg' calling and called lines including a twoavay trunk line having an automatic switch at each end. a common operating circuit for said switches superimposed upon talking conductors of said trunk line. a source of current for said circuit. a signal at each end of said trunk line, and means controlled bv :1 called line at one end of said trunk line for operating the signal at the other end by altering the current How in said circuit.

95. In a telephone system, two exchanges connected by a trunk line terminating at each end in an automatic switch, a controlling circuit superimposed on said trunk line and having at each end a normally connected branch containing a relay for controlling the automatic switch at that end, a source of current for said controlling circuit, circuits at each exchange adapted for connection to said trunk line, supervisory signals associated with said circuits, a normally disconnected branch at each end of said controlling circuit containing a supervisory control relay, means for connecting one of said circuits at either exchan e with said trunk line, automatic means or then sub stituting the normally disconnected branch at that exchange for the normally connected branch, and means for suitably controlling the current flow in said controlling circuit at proper times to effect through the medium of the controlling relay at one end and the supervisory control relay at the other end the operation of the automatic switch at one exchange and the signal associated with the connected circuits at the other exchange.

96. In a telephone system, two exchanges connected by a trunk line terminating at each end in an automatic switch, a controllin circuit superimposed on said trunk line an having at each end a normally connected branch containing a relay for controlling the automatic switch at that end, a source of current for said controlling circuit, circuits at each exchange adapted for connection to said trunk line, supervisory signals associated with said circuits, a normally disconnected branch at each end of said con trolling circuit containing a supervisory control relay, means for connecting one of said circuits at either exchange with said trunk line, automatic means for then substituting the normally disconnected branch at that exchange for the normally connected branch, means associated with the connected circuit at the one exchange for interrupting he controlling circuit to operate the controlling relay at the other exchange, and means at the said other exchange for altering the current flow in said controlling circuit for operating the supervisory control relay at the said first exchange.

97. In a trunking system, a pair of conductors, a first bridge across said conductors, a second bridge across said conductors, a third bridge, means for closing said third bridge across said first and second bridges,

a first relay associated with said third bridge, a line, an automatic progressively movable switch, means for controlling said first relay over said third bridge to operate said switch to find said line, a second relay associated with .said third bridge, a signal associated with said second relay, and means controlled over said line for operating said second I'( lay by way of the third bridge for operating said signal.

98. In a trunking system, a pair of conductors, a first bridge across said conductors, a second bridge across said conductors, a third bridge, means for closing said third bridge across said first and second bridges, a source of current in said third bridge, a first lin'c, a second line, a first relay associated with said third bridge, means controlled over the first line for controlling said 99. In a trunking system, a pair of conductors, a first bridge across said conductors, a second bridge across said conductors, a third bridge, means for closing said third bridge across said first and second bridges, a source of current included in said third brid e, a first relay associated with said thirr bridge, a lire, an automatic pro ressively movable switch, means for controlling said first relay over said third bridge to operate said switch to find said line, a second relay associated with said third bridge, a signal associated with said second relay, said second relay normally inoperative, and means controlled over said line for increasing the flow of current in said third bridge whereby said second relay may be operated to control said signal.

100. In a trunking system, a pair of conductors, a first bridge across said conductors, a second bridge across said conductors, a third bridge, means for closing said third bridge across said first and second bridges, a source of current in said third bridge, a first line, a second line, a first relayi associated with said third bridge, means controlled over the first line for controlling said first relay over said third bridge to operate said switch to connect the two lines by way of said conductors, a second relay associated with said third bridge, a signal associated with said second relay. said second relay normally inoperative, and means controlled over said second line for increasing the flow of current in said third brid e whereby said second rcla y may be operate to control said signal.

101. In a telephone system, a trunk line, operators equipment including a manual connective terminal at each end of said trunk line, an automatic switch at each end of said trunk line and controllable thcreovcr, and means including said equipment and said switches for completing connections over said trunk line semi-automatically in either direction.

102. in a telephone system, a two-Way trunk l ne provided with a manual connective terminal at each end, means including one of said terminals and an automatic switch at the other end of said trunk line controllable thercover for completing con nections over said trunk line in one direction, and means including the other of said terminals and an automatic switch at the other end of said trunk line controllable thcreover for (xnnpleting connections over said trunk line in the opposite direction.

103. In a telephone system, a trunk line, operatofs equipmentincluding a manual connective terminal at each end of said trunk line, an automatic switch at each end of said trunk line and controllable thereovcr. means including said equipment amt said switches for completing connections over said trunk line semi-automatically in either direction, and means for rendering, the said trunk line busy to operators at either end thereof whenever the automatic switch at the same end is operated.

10 in a telephone system, a two-way trunk line provided with a manual connective terminal at each end, means including one of said terminals and an autoillalie switch at the other end of said trunk line controllable tbercover for completing eonnet-tions over said trunk line in one direction, means including the other of said terminals aml an automatic switch at the other end of said trunk line controllable thereover for completing connections over said trunk line in lllttJllllJUSllt. direction,

and means for rendering the said trunk line busy to operators at either end thereol' whenever the automatic switch at the same end is operated.

105. In a telephone. system, a trunk line, operators equipment including a manual connective terminal at each end of said trunk line, an automatic switch at each end of said trunk line and controllable thereover. means including said equipment and said switches for completing connections ouer said trunk line scmi-autoumtically in either direction, and means for rendering, the automatic switch at, either end inoperative whenever the, trunk line is taken for use by an operator at the same end.

I06. in a telephone system, a two-way trunk line provided with a manual conncctive terminal at cachend. means including one of said terminals and an automatic switch at the other-end of said trunk line controllable thcrcovcr for completing (2onticctions o\'cr said trunk line in one diree lion. means including the other of said terminals and an automatic switch at the other end of said trunk line controllable lllcl'tlllt'l for completing connections over said trunk line in the, opposite direction, amt means for rendering the. automatic switch at either end inoperative whenever the trunk line is taken for use by an operator at the sameend.

107. In a telephone system, a two-way trunk line provided with a manual coilnective terminal at each end, means including onepit' said terminals and an automatic switch at the other end of said trunk line' controllable thereover for completing con-. nections over said trunk line in one direction, means including the other of said terminals and an automatic switch at the other end of said trunk line controllable thereover for completing eomiections over said'trunk line in the opposite direction, and operators equipment for completing, connections over said trunk line manually by way of the said terminals.

108. In a telephone system, a two-way trunk line provided with a manual connective terminal at each end. means including one of said terminals and an automatic switch at the other end of said trunk line controlled thereover for completing connections over said trunk line in one direction, means including the other of said terminals and an antomal ic switch at the other end of suidtrunk line controllable. thereover for completing' connections over said trunk line in the opposite direction, opcratofls equi ment for completing connections over said trunk line manually by way of the said terminals. and means for rendering the said trunk line busy to an operator at either end whenever the automatic switch at the same eml is operated.

109. In a telephone system, a two-way trunk line provided with a manual connective terminal at each cud, means including one of said terminals and an automatic switch at the other end ol said trunk line controllable thereorer for completing ICOIlnet-tions over said trunk line in one direction. means including the other of .said terminnls and an automatic switch at the other end of said trunk line controllable lhercorer l'or comp|etin; connections over said trunk line in the'opposite direction, opcrators equipment for completing connections over said trunk line manually by \\a of the said terminals. aml means for rendering the automatic switch at eithei end inopcrat ire whenever the trunk line is taken for use by an operator at the same end.

ll t. In a telephone system. a two-way trunk line. an automatic switch at each end of said trunk line for extending connection therefrom. and menus for controlling the. switch at either end from the other end ovcr the two sides rah-said trunk line in parallel.

lll. In a telephone system. a two-way trunk line. operatofs equipment and an automatic switch at each end of said trunk line. and means controlled by an operator at either end of said trunk line for operat- 

